The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Gas-fired heating units or furnaces that operate at two or more gas flow rates are generally referred to as multistage furnaces. Multistage furnaces are frequently selected by homeowners over single stage furnaces because they offer increased performance and comfort by varying the level of heating output as needed. In many multistage furnaces, a furnace control may be configured to request operation of a gas valve at a desired operating capacity level or gas flow rate. The operating capacity level requested by such furnace controls could be as low as 30 percent of full capacity gas flow operation. However, at low capacity gas flow rates, such gas valves are not capable of controllably maintaining the gas flow rate within a desired tolerance, and therefore are not utilized at such low capacity levels. Accordingly, a need still exists for an improved valve unit and associated control for present two stage heating systems.